Formation of a transitory oval distortion in the primary disc material during a minor merger. The time evolution of the surface density map of the primary disc material of model M6PsRs is plotted, using a face-on view of the initial primary galaxy (experiment f in Table 3). Time is shown at the top left corner of each panel in simulation units. A rainbow colour palette is used to represent different surface density levels in logarithmic scale, with redder colours indicating higher values. All physical quantities are given in simulation units. The major axis of the oval distortion formed in the remnant disc by the satellite impact is marked with a black line in the last panels. It rotates in the same direction as the primary disc material (clockwise). The orbit and rotation of the accreted satellite is counter-clockwise. The time life of this bar-like distortion corresponds to  ~0.3 Gyr, using the scaling indicated in Sect. 2.